Reaction entropy measurements for transition-metal ions bound to nation-coated electrode surfaces

Charles M. Lieber, Michael H. Schmidt, Nathan S Lewis

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Reaction entropies, ΔS°rc, have been determined for a series of transition-metal ions electrostatically bound into Nafion films. Complexes with hydrophobic, "shielding" ligands such as Ru(2,2′-bipyridine)3 3+/2+ and Co(2,2′-bipyridine)3 3+/2+ yield similar ΔS°rc values in Nafion films and in aqueous solution, indicating that the electrochemically active probes reside in a predominantly waterlike local environment in the polymer film. Complexes containing aquo and ammine ligands yield markedly lower ΔS°rc values in Nafion than in aqueous media (μ = 0.1 M). The ΔS°rc values for these Nafion-bound systems are similar to values measured for the Ru(NH3)6 3+/2+ system in concentrated aqueous salt solutions (5 M LiCl). The ΔS°rc measurements imply that the outer-sphere electron-transfer work terms for polymer bound ions may be lower than those observed in typical aqueous solutions. Differential free energies, enthalpies, and entropies of transfer for the redox reaction M(III) + e- → M(II) from aqueous media to Nafion have also been determined.

Original languageEnglish
Pages (from-to)1002-1003
Number of pages2
JournalJournal of Physical Chemistry
Issue number6
Publication statusPublished - 1986

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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